[time-nuts] Thermal insulation choice?

[John Ackermann N8UR]

I am looking for a readily available (from Home Depot or other local 
source) insulating material to use in a chassis that's housing a 
sensitive OCXO.  My goal is just to slow down any external thermal 
transients so the oven loop has time to react gracefully.

I'm thinking of something in sheet form that I could glue to the inside 
bottom and side of the metal chassis.  The trimmed sheet sizes will each 
probably end up being around 4 x 8 inches.  I have enough clearance for 
a thickness of a half inch or so.  I'd like to avoid a bat material as 
that would be hard to mount neatly.

Long lifetime (ie, not getting all crumbly after a few years) is 
important as I don't expect this oscillator to get cold until I do.

Any suggestions of a material to look for?

Thanks,

John